1. Field of the Invention
The present invention relates to a method and apparatus for piecing slivers in a textile machine such as a roving frame.
2. Description of Related Art
Japanese Un-Examined Patent Publication (Kokai) No. 2-91233 discloses an automatic apparatus for piecing a sliver from a full can to a sliver which is fed from a consumed can to a roving frame. In this prior art apparatus, the piecing of slivers is executed when the spinning operation of the sliver is stopped. Namely, first, the sliver from the consumed can to the corresponding drafting unit of the roving frame is broken. Then, the broken end from the drafting unit is, at a piecing unit, superimposed with an end of a sliver from the full can. The piecing unit is, then, operated for piecing the superimposed ends of the sliver. Such a piecing operation is repeated for all of the cans of the roving unit. After the completion of the piecing operation for all of the cans of the roving frame, a spinning operation by the roving frame is re-started.
Japanese Un-Examined Patent Publication (Kokai) No. 4-49176 discloses an automatic piecing unit wherein the end from the drafting unit of a roving frame and the end from a full can are nipped by a nipping means, so that the superimposed ends are interwound by imparting air flows. In Japanese Un-Examined Patent Publication (Kokai) No. 3-232669, spikes are provided for causing the fibers between the combined slivers to be interwound. Furthermore, the Japanese Un-Examiner Patent Publication (kokai) No. 4-163328 (corresponding to U.S. Pat No. 5,177,835) discloses a system for an automatic piecing of slivers in a textile machine, such as a roving frame, wherein it has a sliver piecing assembly having a plurality of sets of opposite, separable draft rollers and a set of separable rubbing rollers at an outlet side of the draft rollers for holding a first old sliver between the opposite rollers. The system is further provided with a sliver feed assembly having an opposite, separable set of feed rollers for holding a second sliver therebetween. The first sliver from a can which is emptied or nearly emptied is held by the opposite rollers of the piecing assembly, and the first sliver is cut between the piecing assembly and the can, in such a manner that a sufficient length of the sliver exists on the inlet side of the piecing assembly to obtain a desired piecing operation. Then, a feeding operation of the first sliver is commenced by rotating the rollers, while a feeding operation of the second sliver from a full can by means of the feeding assembly is also commenced so that a front end of the second assembly is introduced into the inlet side of the piecing assembly so that the second sliver from the can is combined with the first sliver from the can which is nearly emptied. When the combined first and second slivers reach the drafting rollers of the piecing assembly, a draft ratio by the drafting rollers, which is a ratio of the rotational speed of the outlet side draft rollers to those of the inlet side draft roller, is changed from a value of 1.0 to 2.0, so that the thickness of the combined sliver is reduced to the thickness corresponding to that for a single sliver, when the combined sliver is moved out of the outlet side drafting rollers. Furthermore, at the outlet side of the draft rollers, the combined slivers are subjected to a rubbing movement by the rubbing rollers which are rotated in opposite directions for feeding the sliver while being oppositely axially reciprocated, which allows the combined slivers to be interwound with each other to provide a complete single sliver.
In the prior arts, the piecing operation of the slivers are done when a feeding of a sliver to the roving frame is interrupted, which makes it impossible to execute the piecing operation when the roving frame is operated. Thus, in order to execute the sliver piecing operation, the spinning operation is interrupted, which reduces the production efficiency of a spinning factory. In the prior arts, fibers are only insufficiently interwound between the combined slivers, which causes a defect to be created at the pieced portion of the sliver, which frequently causes the sliver to be broken at a following spinning process. Furthermore, in the prior arts, the thickness of the pieced portion of the sliver is apt to be rapidly increased from a thickness of a single sliver, which causes the combined sliver to become uneven, which causes the quality of the pieced portion to be worsened, thereby sliver to be easily broken at a subsequent process.